Magnetic sensor and magnetic measurement device

Abstract

To provide a magnetic sensor and magnetic measurement device, which suppress gain fluctuation in conversion from external magnetism to an output signal.SOLUTION: A magnetic sensor is provided, comprising a magnetism detection unit configured to output a detection signal corresponding to external magnetism, a signal processing unit configured to generate an output signal by applying given signal processing to the detection signal, and a stabilizing unit provided with a current generation unit configured to generate a feedback current based on the output signal and output the same to the magnetism detection unit and configured to suppress gain fluctuation in conversion from the external magnetism to the output signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic sensor and a magnetic measurement device. [Background technology]

[0002] The following Patent Document 1 discloses a magnetic sensor and a biomagnetic measuring device capable of accurately detecting an induced voltage corresponding to an external magnetic field when one pickup coil is used to detect the induced voltage and generate a bias magnetic field.

[0003] This background technology employs a solution comprising a sensor head having a magnetic material, a drive unit that passes current through the sensor head, a pickup coil in close proximity to the sensor head, and an information processing unit that generates a bias magnetic field by passing current through the pickup coil and detects a signal corresponding to the voltage generated in the pickup coil, wherein the information processing unit generates a differential signal indicating the difference between a first signal corresponding to the voltage generated in the pickup coil when the sensor head is in an energized state and a second signal corresponding to the voltage generated in the pickup coil when the sensor head is in a non-energized state and not energized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-100056 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the above-mentioned background art employs a magnetic feedback method for generating a bias magnetic field, which generates a bias magnetic field in opposite phase to the external magnetic field by feeding back (feeding back) a current according to an output signal to a pickup coil. Specifically, in the background art, the output signal is converted into a current using a resistor that functions as a current generator, and the current is fed back to the pickup coil.

[0006] When using such magnetic feedback, the conversion gain from a magnetic signal to an electric signal, from the detection of an external magnetic field (external magnetism) by a pickup coil to the generation of an output signal, is determined mainly by the accuracy of a current generator (current generating unit) provided in the feedback path. However, this current generator has a problem in that the output current varies due to manufacturing variations, temperature, etc., and therefore the conversion gain of the magnetic measuring device varies.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a magnetic sensor and a magnetic measuring device that are capable of suppressing fluctuations in the conversion gain from an external magnet to an output signal. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention adopts, as a first solution relating to a magnetic sensor, a magnetic detection unit that outputs a detection signal corresponding to an external magnetic field, a signal processing unit that generates an output signal by performing a predetermined signal processing on the detection signal, and a current generating unit that generates a feedback current based on the output signal and outputs it to the magnetic detection unit, and a stabilization unit that suppresses fluctuations in the conversion gain from the external magnetic field to the output signal.

[0009] The present invention employs a second solution related to a magnetic sensor, in which, in the above-mentioned first solution, the stabilization unit includes a comparison unit that compares the feedback current with a predetermined reference current, and a correction signal generation unit that generates a correction signal that suppresses fluctuations in the conversion gain based on the comparison result of the comparison unit.

[0010] The present invention provides a third solution related to a magnetic sensor, which is the same as the second solution, in which the stabilization unit controls the current generating unit based on the correction signal so that the feedback current is equal to the reference current.

[0011] The present invention provides a fourth solution related to a magnetic sensor, which is the same as the second solution, in which the stabilization unit applies a correction process to the output signal based on the correction signal so that the feedback current is equal to the reference current.

[0012] The present invention employs a fifth solution related to a magnetic sensor, in which in any of the first to fourth solutions above, the current generating unit includes a high-voltage side current generator connected to the high-voltage side of the magnetic detection unit and generating the feedback current based on the output signal, and a low-voltage side current generator connected to the low-voltage side of the magnetic detection unit and generating the feedback current based on the output signal.

[0013] The present invention employs a sixth solution related to a magnetic sensor, which is any one of the first to fifth solutions above, in which the output signal is a digital signal, and the current generating unit generates the feedback current by digital / analog converting the output signal.

[0014] The present invention employs, as a seventh solution related to the magnetic sensor, any one of the first to sixth solutions, wherein the comparison section has a hysteresis characteristic in comparing the feedback current with the reference current.

[0015] The present invention employs an eighth solution relating to a magnetic sensor, in which in any one of the first to seventh solutions above, the magnetic detection unit includes a pickup coil that detects the external magnetic field, and a magnetic feedback coil through which the feedback current is passed.

[0016] The present invention employs, as a ninth solution relating to the magnetic sensor, any one of the first to eighth solutions, in which the magnetic detection portion is a magnetic impedance element.

[0017] In the present invention, as a first solution related to a magnetic measurement device, a solution is adopted in which the magnetic measurement device includes a magnetic sensor related to any one of the first to eighth solutions, and a magnetic measurement unit that measures magnetism using the output signal.

[0018] The present invention employs, as a second solution relating to the magnetic measurement device, the solution according to the first solution relating to the magnetic measurement device, in which the external magnetism is biomagnetism generated in a living body. Effect of the Invention

[0019] According to the present invention, it is possible to provide a magnetic sensor and a magnetic measurement device capable of suppressing fluctuations in the conversion gain from an external magnet to an output signal caused by manufacturing variations and environmental changes. [Brief description of the drawings]

[0020] [Figure 1] 1 is a block diagram showing a configuration of a magnetic sensor A1 according to a first embodiment of the present invention. [Diagram 2] 1 is a block diagram showing a main configuration of a first embodiment of the present invention, that is, a configuration of a stabilization section B1. FIG. [Diagram 3] 1 is a block diagram showing a configuration of a magnetic measurement device C1 according to a first embodiment of the present invention. [Figure 4] 4 is a timing chart showing the operation of a main part of the magnetic sensor A1 according to the first embodiment of the present invention, that is, the operation of the stabilization part B1. [Diagram 5] FIG. 11 is a block diagram showing a configuration of a magnetic sensor A2 according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a block diagram showing a configuration of a magnetic sensor A3 according to a third embodiment of the present invention. [Figure 7] FIG. 13 is a block diagram showing a configuration of a current generating section in a first modified example of the present invention. [Figure 8] FIG. 13 is a block diagram showing a configuration of a stabilization section B4 in a first modified example of the present invention. [Figure 9] FIG. 13 is a block diagram showing a configuration of a stabilization unit B5 in a second modified example of the present invention. [Figure 10] FIG. 13 is a block diagram showing a configuration of a current generating section B6 in a second modified example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [First embodiment] First, a first embodiment of the present invention will be described with reference to FIGS. 1, the magnetic sensor A1 according to the first embodiment includes a sensor head 1, a driving unit 2, a pickup coil 3, a signal processing unit 4, a current generating unit 5, a comparing unit 6, and a correction signal generating unit 7. Among these components, the current generating unit 5, the comparing unit 6, and the correction signal generating unit 7 configure the stabilizing unit B1 in the first embodiment.

[0022] The sensor head 1 is a two-terminal element with one end connected to the output end of the driver 2 and the other end grounded. This sensor head 1 is made of a magnetic material whose magnetic properties change when a drive voltage is applied from the driver 2 while an external magnetic field G is acting on it. That is, in this sensor head 1, a magnetization change according to the strength (magnitude) of the external magnetic field G, that is, a magnetic flux change, occurs in the sensor head 1.

[0023] Here, the sensor head 1 constitutes a magnetic impedance element together with a pickup coil 3 described later. That is, the sensor head 1 in the first embodiment is, for example, an amorphous wire. When a driving voltage is applied to the sensor head 1 from the driving unit 2 in a state where an external magnetic field G acts on the sensor head 1, the impedance of the sensor head 1 changes, and the magnetic flux penetrating the inside of the sensor head 1 changes. The amount of change in this impedance depends on the magnitude of the external magnetic field G.

[0024] The driver 2 has an output end connected to one end of the sensor head 1, and applies a predetermined drive voltage from the output end to one end of the sensor head 1. This driver 2, together with the above-mentioned magnetic impedance element (sensor head 1 and pickup coil 3), constitutes the magnetic detection unit of the present invention. Such driver 2 is a voltage source that generates a fluctuating voltage, such as a pulse voltage or a high-frequency voltage, and applies the fluctuating voltage to the sensor head 1 for driving the sensor head 1.

[0025] The pickup coil 3 is a winding wound around the sensor head 1. One end of the pickup coil 3 is connected to one input end (first input end) of the signal processing unit 4 and an output end of the current generating unit 5, and the other end is connected to the other input end (second input end) of the signal processing unit 4 and the first input end of the current generating unit 5.

[0026] Such a pickup coil 3 is wound around the sensor head 1, and the change in magnetic flux on the surface of the sensor head 1 in response to an external magnetic field appears as an induced voltage at both ends of the coil through the pickup coil 3. This induced voltage corresponds to the detection signal of the present invention, and as shown in the figure, a high-voltage side detection voltage V P and the low-voltage side detection voltage V generated at the other end of the pickup coil 3. N This induced voltage is the difference voltage between the input voltage V in The signal is input to the signal processing unit 4 as the signal.

[0027] FIG. 1 shows a resistor R connected in series with the pickup coil 3. p This resistor R p is a parasitic resistance that is inevitably parasitic on the pickup coil 3 and has a certain resistance value (parasitic resistance value). That is, when a current is applied to the pickup coil 3, the resistor R p A parasitic voltage corresponding to the parasitic resistance value is generated across both ends of the resistor.

[0028] As described in a well-known document (JP 2022-100055 A), this parasitic voltage is a factor of error in the detection of the external magnetic field G by the sensor head 1, the driving unit 2, and the pickup coil 3. That is, as described in the above-mentioned well-known document, it is preferable to subtract it from the induced voltage induced in the pickup coil 3.

[0029] The signal processing unit 4 has a first input terminal connected to one end of the pickup coil 3 and an output terminal of the current generating unit 5, and a second input terminal connected to the other end of the pickup coil 3 and a first input terminal of the current generating unit 5. In addition, the output terminal of the signal processing unit 4 is connected to the second input terminal of the current generating unit 5 and the first input terminal of the correction signal generating unit 7.

[0030] Such a signal processing unit 4 converts the induced voltage induced in the pickup coil 3 into an input voltage V in And this input voltage V in By applying a predetermined signal processing to the 0 That is, this output signal D 0 is a signal indicating the strength (magnitude) of the external magnetic field G. The signal processing unit 4 outputs the output signal D 0 and outputs it to the outside and to the second input terminal of the current generating unit 5.

[0031] This output signal D 0 Although the output signal D0 may be either an analog signal or a digital signal, it is a digital signal in the first embodiment. That is, the output signal D0 is a binary code of N bits (N: natural number) indicating the strength (magnitude) of the external magnetic field G, and is configured as a bit string from the 0th bit to the N-1th bit. Note that such an output signal D 0 More precisely, in addition to the above binary codes, it also includes binary codes that are phase-inverted versions of the above binary codes (inverted binary codes).

[0032] The current generating unit 5 has a third input terminal in addition to the first and second input terminals described above. The first input terminal of this current generating unit 5 is connected to the other terminal of the pickup coil 3 and the second input terminal of the signal processing unit 4, the second input terminal is connected to the output terminal of the signal processing unit 4 and the first input terminal of the correction signal generating unit 7, and the third input terminal is connected to the output terminal of the correction signal generating unit 7.

[0033] The current generating section 5 receives the output signal D 0 (Digital signal) based on magnetic feedback current I fb The current generating unit 5 is a D / A converter (digital / analog converter) that generates an output signal D 0 The magnetic feedback current I generated based on fb The correction signal D is adjusted so that the ctrl Using the magnetic feedback current I fb Fine tune the.

[0034] The comparison unit 6 has an input terminal connected to the output terminal of the current generation unit 5, the pickup coil 3, and a first input terminal of the signal processing unit 4, and an output terminal connected to the input terminal of the correction signal generation unit 7. The comparison unit 6 detects the magnetic feedback current I fb Feedback voltage based on V P and the internally generated reference current I REF Based on the reference voltage V r Compare with.

[0035] Here, the comparison unit 6 in the first embodiment detects the magnetic feedback current I fb and the reference current I REF Instead of directly comparing the feedback voltage V P and the reference voltage V r and based on the magnetic feedback current I fb and the reference current I REF That is, the comparison unit 6 indirectly compares the magnetic feedback current I fbThe feedback voltage V is based on the voltage drop across the resistor caused by the current flowing through the resistor. P and the reference current I REF A reference voltage V is based on the voltage drop across another resistor caused by the current passing through r This is a comparison with.

[0036] In addition, the comparison unit 6 detects the feedback voltage V P and the reference voltage V r In other words, the comparison unit 6 has a hysteresis characteristic in comparison with the feedback voltage V P and the reference voltage V r In order to prevent the output from repeatedly switching between "H (high level)" and "L (low level)" when the values ​​of these are close to each other, the first threshold voltage when the output transitions from "H (high level)" to "L (low level)" is different from the second threshold voltage when the output transitions from "L (low level)" to "H (high level)."

[0037] Such a comparison unit 6 detects the feedback voltage V P and the reference voltage V r The comparison result with the magnetic feedback current I fb and the reference current I REF A step signal that indicates the magnitude relationship with the comparison signal V comp to the correction signal generating unit 7. This comparison signal V comp is the voltage at which the output is fed back to the feedback voltage V P and the reference voltage V r It changes to "H (high level)" or "L (low level)" depending on the magnitude relationship with

[0038] The correction signal generating unit 7 has a first input terminal connected to the output terminal of the signal processing unit 4 and a second input terminal of the current generating unit 5, a second input terminal connected to the output terminal of the comparing unit 6, and an output terminal connected to the third input terminal of the current generating unit 5. The correction signal generating unit 7 converts, for example, the output signal D 0 (digital signal) and the comparison signal V input from the comparison unit 6 to the second input terminal comp By carrying out a predetermined logic process on each of them, a correction signal Dctrl Generate.

[0039] That is, the correction signal generating unit 7 generates the correction signal D ctrl By controlling the current generating unit 5 using 0 (digital signal) to magnetic feedback current I fb The correction signal D ctrl is the comparison signal V input from the comparison unit 6 to the correction signal generation unit 7. comp Since it is generated based on the feedback voltage V P is the reference voltage V r That is, the magnetic feedback current I fb is the reference current I REF The current generating unit 5 is controlled so that the current becomes equal to

[0040] The above-mentioned current generating section 5, comparing section 6, and correction signal generating section 7 constitute a stabilizing section B1 in the first embodiment. 0 (digital signal) is used as the input signal, and the magnetic feedback current I fb That is, the stabilization unit B1 outputs the output signal D 0 (digital signal) based on a constant value (reference current I REF ) the magnetic feedback current I fb is generated and output to the pickup coil 3.

[0041] Next, a specific configuration of the stabilization unit B1 will be described with reference to FIG. As shown in the figure, the stabilization unit B1 includes N high-voltage side resistance cells 10, N low-voltage side resistance cells 11, two reference cells 12, a constant current source 13, a comparator 14, and a logic circuit 15 (Logic).

[0042] Of these components, the N high-voltage side resistance cells 10 and the N low-voltage side resistance cells 11 constitute the above-mentioned current generating unit 5. The N high-voltage side resistance cells 10 correspond to the high-voltage side current generator in the present invention, and the N low-voltage side resistance cells 11 correspond to the low-voltage side current generator in the present invention. In addition, the two reference cells 12, the constant current source 13 and the comparator 14 constitute the above-mentioned comparison unit 6. Furthermore, the logic circuit 15 corresponds to the above-mentioned correction signal generating unit 7.

[0043] The high-voltage side resistor cell 10 and the low-voltage side resistor cell 11 output the above-mentioned output signal D 0 That is, N high-voltage side resistor cells 10 are provided corresponding to the bit string from the 0th bit to the (N-1)th bit. That is, the N high-voltage side resistor cells 10 are 0 The 0th bit of the high-voltage resistor cell corresponds to the 0th bit of the output signal D 0 The first high-voltage side resistor cell corresponding to the first bit of the 0 The N-1th high-voltage side resistor cell corresponds to the N-1th bit of the N-1th high-voltage side resistor cell.

[0044] The N high-voltage side resistance cells 10 all have the same circuit configuration, and as shown in the figure, include a high-voltage side switch 10a, a low-voltage side switch 10b, a variable resistor 10c, and an enable switch 10d. Also, the N low-voltage side resistance cells 11 all have the same circuit configuration, and as shown in the figure, include a high-voltage side switch 11a, a low-voltage side switch 11b, a variable resistor 11c, and an enable switch 11d.

[0045] The high-voltage side switch 10a is a two-contact open / close switch with a first contact connected to a DC power supply, a second contact connected to the first contact of the low-voltage side switch 10b and one end of the variable resistor 10c, and a control end connected to the control end of the high-voltage side switch 11a and the control end of the low-voltage side switch 11b in the low-voltage side resistor cell 11 and the first input end of the logic circuit 15.

[0046] Further, the control terminal of the high-voltage side switch 10a is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilizing unit B1. The high-voltage side switch 10a receives the output signal D 0 is input and the output signal D 0 The open / closed state is controlled by.

[0047] That is, the high-voltage side switch 10a of the first high-voltage side resistor cell receives the output signal D 0 The high-voltage side switch 10a of the first high-voltage side resistor cell is controlled by the 0th bit of the output signal D 0 The open / closed state of high-voltage side switch 10a of the (N-1)th high-voltage side resistor cell is controlled by the (N-1)th bit of the output signal D0.

[0048] Low-voltage-side switch 10b is a two-contact open / close switch similar to high-voltage-side switch 10a. A first contact of low-voltage-side switch 10b is connected to the second contact of high-voltage-side switch 10a and one end of variable resistor 10c, a second contact is grounded, and a control end is connected to the control end of high-voltage-side switch 11a and the control end of low-voltage-side switch 11b in low-voltage-side resistor cell 11 and a first input end of logic circuit 15.

[0049] The control terminal of the low-voltage side switch 10b is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilizing unit B1. 0 (digital signal) is input, and this output signal D 0 The open / closed state is controlled inversely to that of high-voltage side switch 10a by the inverted sign of the (digital signal).

[0050] That is, the low-voltage side switch 10b of the first highest-voltage side resistance cell receives the output signal D 0 The open / close state is controlled by the inversion code of the 0th bit in the 1st high-voltage side resistor cell, and the low-voltage side switch 10b of the 1st high-voltage side resistor cell is 0The open / close state is controlled by the inverted sign of the first bit in (omitted), and the low-voltage side switch 10b of the N-1th high-voltage side resistor cell is 0 The open / close state is controlled by the inversion sign of the (N-1)th bit in

[0051] Variable resistor 10c is a three-terminal resistive element having a predetermined resistance variable range. One end of variable resistor 10c is connected to the second contact of high-voltage side switch 10a and the first contact of low-voltage side switch 10b, and the other end is connected to the first contact of enable switch 10d.

[0052] The variable resistor 10c has a control terminal commonly connected to the control terminal of the variable resistor 11c in the low-voltage side resistance cell 11 and the control terminal of the variable resistor 12a in the reference cell 12. The variable resistor 10c is connected to the control terminal of the correction signal D ctrl The resistance value is variably set in a discrete manner.

[0053] The enable switch 10d is a two-contact open / close switch, with a first contact connected to the other end of the variable resistor 10c and a second contact serving as an input / output terminal for connecting to the outside of the high-voltage side resistance cell 10. The second contact (input / output terminal) of the enable switch 10d is commonly connected to the input / output terminals of all the high-voltage side resistance cells 10 as shown in the figure.

[0054] In addition, a second contact (input / output terminal) of the enable switch 10d is also connected to one end of the pickup coil 3, a first input terminal of the signal processing unit 4, and a first input terminal of the comparator 14. The open / closed state of the enable switch 10d is controlled by an enable signal EN (not shown).

[0055] The enable signal EN controls the magnetic feedback current I fb The enable signal EN is a control signal that turns on (power supply) / off (power non-supply) the power supply to the pickup coil 3. In the normal state, the enable signal EN sets the enable switch 10d to the ON state (closed state) and controls the magnetic feedback current Ifb The high-voltage side resistance cell 10 is set in a state in which power is supplied to the pickup coil 3.

[0056] On the other hand, the N low-voltage side resistor cells 11 output the output signal D 0 The 0th bit of the low-voltage resistor cell LS 0 , output signal D 0 The first low-voltage side resistor cell LS corresponding to the first bit of 1 , (omitted), Output signal D 0 The N-1st low-voltage side resistor cell LS corresponding to the N-1st bit of N-1 It consists of:

[0057] In the N low-voltage side resistance cells 11, the high-voltage side switch 11a is a two-contact open / close switch, similar to the high-voltage side switch 10a of the high-voltage side resistance cell 10. The first contact of this high-voltage side switch 11a is connected to a DC power source, and the second contact is connected to the first contact of the low-voltage side switch 11b and one end of the variable resistor 11c.

[0058] The control terminal of the high-voltage side switch 11a is connected to the control terminal of the high-voltage side switch 10a and the control terminal of the low-voltage side switch 10b in the high-voltage side resistance cell 10, and to the first input terminal of the logic circuit 15. The high-voltage side switch 11a is connected to the first high-voltage side resistance cell HS 1 Similarly to the low-voltage side switch 10b in 0 The open / closed state is controlled by the inversion sign of

[0059] That is, the first low-voltage resistance cell LS 1 The high-voltage side switch 11a in 0 The open / close state is controlled by the inversion code of the 0th bit of the low-voltage side resistor cell HS 1 The high-voltage side switch 11a of the output signal D 0 The open / close state is controlled by the inversion code of the first bit of the N-1th low-voltage side resistor cell HS N-1 The high-voltage side switch 11a of the output signal D 0The open / close state is controlled by the inverted sign of the (N-1)th bit.

[0060] Like high-voltage side switch 11a, low-voltage side switch 11b is a two-contact open / close switch. A first contact of low-voltage side switch 11b is connected to the second contact of high-voltage side switch 11a and one end of variable resistor 11c, and a second contact is grounded.

[0061] The control terminal of the low-voltage side switch 11b is connected to the control terminal of the high-voltage side switch 10a and the control terminal of the low-voltage side switch 10b in the high-voltage side resistance cell 10, and to the first input terminal of the logic circuit 15. The low-voltage side switch 11b is connected to the first high-voltage side resistance cell HS 1 Similarly to the high-voltage side switch 10a in 0 The open / closed state is controlled by.

[0062] That is, the first low-voltage resistance cell LS 1 The low-voltage side switch 11b of the output signal D 0 The open / close state is controlled by the 0th bit in the 1 The low-voltage side switch 11b of the output signal D 0 The open / close state is controlled by the first bit in (omitted), and the N-1th low-voltage side resistor cell LS N-! The low-voltage side switch 11b of the output signal D 0 The open / close state is controlled by the N-1th bit in

[0063] Variable resistor 11c is a two-terminal resistive element having a predetermined resistance variable range. One end of variable resistor 11c is connected to the second contact of high-voltage side switch 11a and the first contact of low-voltage side switch 11b, and the other end is connected to the first contact of enable switch 11d.

[0064] The variable resistor 11c has a control terminal commonly connected to the control terminal of the variable resistor 10c in the high-voltage side resistor cell 10 and the control terminal of the variable resistor 12a in the reference cell 12. The variable resistor 11c is connected to the control terminal of the correction signal D ctrl The resistance value is variably set by

[0065] The enable switch 11d is a two-contact open / close switch, with a first contact connected to the other end of the variable resistor 11c and a second contact serving as an input / output terminal for connecting to the outside of the low-voltage side resistance cell 11. The second contact (input / output terminal) of the enable switch 11d is commonly connected to the input / output terminals of all the low-voltage side resistance cells 11 as shown in the figure.

[0066] The second contact (input / output terminal) of the enable switch 11d is also connected to the other end of the pickup coil 3 and the second input terminal of the signal processor 4. The open / close state of the enable switch 11d is controlled by the enable signal EN described above. This enable signal EN is supplied to the enable switch 11d via a control circuit that controls the magnetic feedback current I fb This is provided to energize the pickup coil 3 for a specific period of time.

[0067] The two reference cells 12 have the same circuit configuration, and each includes a variable resistor 12a. The variable resistor 12a is a two-terminal resistive element having a predetermined resistance variable range. One end of the variable resistor 12a is connected to a DC power source, and the other end is connected to an input terminal of a constant current source 13 and a second input terminal of a comparator 14.

[0068] The variable resistor 12a has a control end commonly connected to the control end of the variable resistor 10c in the high-voltage side resistance cell 10 and the control end of the variable resistor 11c in the low-voltage side resistance cell 11. The variable resistor 12a, like the variable resistor 10c in the high-voltage side resistance cell 10 and the variable resistor 11c in the low-voltage side resistance cell 11, receives the correction signal D input to the control end from the logic circuit 15 (correction signal generating unit 7). ctrl The resistance value is variably set by

[0069] The constant current source 13 is a two-terminal element having an input terminal and an output terminal. The input terminal of this constant current source 13 is connected to the other terminal of the variable resistor 12a and the second input terminal of the comparator 14, and the output terminal is grounded. Such a constant current source 13 has a reference voltage V r When a constant reference current I is applied from the input terminal to the output terminal, REF Force the water to flow.

[0070] Here, the reference voltage V r is the power supply voltage V of the DC power supply cc , the set resistance value R of the variable resistor 12a r and the reference current I REF That is, the reference voltage Vr is determined by the power supply voltage V applied to one end of the variable resistor 12a. cc is the set resistance value R of the variable resistor 12a r and the reference current I REF This is the voltage drop obtained by multiplying

[0071] The comparator 14 is a three-terminal element having a pair of input terminals (a first input terminal and a second input terminal) and one output terminal. Of the first input terminal and the second input terminal, the first input terminal is a negative phase input terminal (-) as shown in the figure, and the second input terminal is a positive phase input terminal (+) as shown in the figure.

[0072] The comparator 14 detects a feedback voltage V P and the reference voltage V applied to the second input r and a comparison signal V comp The comparison signal V comp is the feedback voltage V P is the reference voltage V r In the above cases, the voltage becomes L level (low voltage), and the feedback voltage V P is the reference voltage V r If the input voltage is smaller than 1, it is a binary signal that is at H level (high potential).

[0073] Logic circuit 15 (Logic) corresponds to the above-mentioned correction signal generating unit 7, and is a two-input, one-output logic circuit. A first input terminal of this logic circuit 15 is connected to the control terminal of high-voltage side switch 10a and the control terminal of low-voltage side switch 10b in high-voltage side resistance cell 10, and the control terminal of high-voltage side switch 11a and the control terminal of low-voltage side switch 11b in low-voltage side resistance cell 11.

[0074] Moreover, a first input terminal of the logic circuit 15 is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilizing unit B1. Moreover, a second input terminal of this logic circuit 15 is connected to the output terminal of the comparator 14. Furthermore, an output terminal of this logic circuit 15 is connected to the control terminal of the variable resistor 10c in the high-voltage side resistance cell 10, the control terminal of the variable resistor 11c in the low-voltage side resistance cell 11, and the control terminal of the variable resistor 12a in the reference cell 12.

[0075] The logic circuit 15 receives the output signal D input from the signal processing unit 4 to the first input terminal. 0 and a comparison signal V input from the comparator 14 to the first input terminal. comp By carrying out a predetermined logical process on the ctrl This correction signal D ctrl is the feedback current I fb is a digital signal indicating the amount of correction.

[0076] The above-mentioned comparator 14 has a hysteresis characteristic as described in the comparison unit 6. In contrast, the logic circuit 15 (correction signal generating unit 7) is configured so as to function even if the comparator 14 (comparison unit 6) does not have a hysteresis characteristic. In other words, the logic circuit 15 has a dead band over a predetermined period, and the correction signal D does not change even if the comparison result of the comparator 14 (comparison unit 6) changes. ctrl Do not update.

[0077] This correction signal D ctrlis output to the current generating unit 5 as a control signal for controlling the current generating unit 5. That is, the correction signal D ctrl is the feedback voltage V P and the reference voltage V r Based on the magnitude relationship with the magnetic feedback current I fb is the reference current I REF The current generating unit 5 is feedback-controlled so that the current becomes equal to

[0078] Here, the current generating unit 5 in the first embodiment is provided with N high-voltage side resistance cells 10 functioning as D / A converters on one end side of the pickup coil 3, and N low-voltage side resistance cells 11 similarly functioning as D / A converters on the other end side of the pickup coil 3. That is, the stabilizing unit B1 in the first embodiment supplies feedback current I fb A circuit configuration is adopted to correct the above.

[0079] Next, the magnetic measurement device C1 according to the first embodiment will be described with reference to FIG. As shown in FIG. 3, the magnetic measurement device C1 includes a plurality of magnetic sensors A1 according to the first embodiment and an output signal D 0 The apparatus includes four magnetic measurement units E1 to E4 that measure magnetism (biomagnetism) generated by a living body using a magnetic sensor. The magnetic sensors A1 detect biomagnetism generated by, for example, various organs in the human body, and detect, for example, magnetism generated by the brain (brain magnetism), magnetism generated by nerves (neuromagnetism), magnetism generated by the heart (cardiac magnetism), and magnetism generated by muscles (muscle magnetism).

[0080] The magnetic sensor A1 for detecting brain magnetism is connected to a first magnetic measurement unit E1, and outputs an output signal D indicative of brain magnetism to the first magnetic measurement unit E1. 0 The magnetic sensor A1 for detecting neuromagnetism is connected to a second magnetic measurement unit E2, and outputs an output signal D indicative of neuromagnetism to the second magnetic measurement unit E2. 0 Output.

[0081] The magnetic sensor A1 for detecting cardiac magnetism is connected to a third magnetic measurement unit E3, and outputs an output signal D indicative of cardiac magnetism to the third magnetic measurement unit E3. 0 The magnetic sensor A1 for detecting muscle magnetism is connected to a fourth magnetic measurement unit E4, and outputs an output signal D indicative of muscle magnetism to the fourth magnetic measurement unit E4. 0 Output.

[0082] The first magnetic measurement unit E1 outputs an output signal D indicative of brain magnetism. 0 The second magnetic measurement unit E2 measures the intensity and distribution of the brain magnetism based on the signal and outputs the signal to the outside. 0 The third magnetic measurement unit E3 measures the intensity and distribution of neuromagnetism based on the signal and outputs the measured signal to the outside. 0 The fourth magnetic measurement unit E4 measures the strength and distribution of the cardiac magnetism based on the signal D, and outputs the measured signal D to the outside. 0 Based on this, the strength and distribution of muscle magnetism are measured and output to the outside.

[0083] According to the magnetic measuring device C1, a stable and high-resolution (picotesla level) biomagnetic measuring device can be realized with small size and low power consumption. That is, according to the magnetic measuring device C1, there is no need to use a known magnetic sensor head (SQUID, etc.) for biomagnetic measurement, and it is possible to realize a significant reduction in size and cost.

[0084] Next, the operations of the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment will be described in detail with reference to the timing chart shown in FIG.

[0085] The first embodiment aims to suppress the fluctuation of the conversion gain of the magnetic sensor A1, thereby improving the measurement accuracy of the magnetic measurement device C1. cc If there is a change in the ambient temperature or the like, the conversion gain of the magnetic sensor A1 may vary due to these variations or changes. When the conversion gain of the magnetic sensor A1 varies, the output current D0 fluctuates, making it impossible to realize stable magnetic detection and measurement.

[0086] In the first embodiment, the stabilization unit B1 having the above-mentioned configuration is provided in the magnetic sensor A1, thereby suppressing fluctuations in the conversion gain of the magnetic sensor A1 and realizing stable magnetic detection and magnetic measurement. The timing chart of FIG. 4 shows the time-series operation of the stabilization unit B1.

[0087] For example, as shown in the top row of Figure 4, the power supply voltage V cc When the magnetic feedback current I fb is the reference current I REF At this time, the output signal D 0 is "2" as shown in the figure, that is, if it matches the number of cells in the reference cell 12, the comparison signal V comp A correction signal D controls the resistance value of the variable resistor 10c in the high-voltage side resistance cell 10, the resistance value of the variable resistor 11c in the low-voltage side resistance cell 11, and the resistance value of the variable resistor 12a in the reference cell 12 in response to the ctrl Update.

[0088] For example, the magnetic feedback current I fb is the reference current I REF In the following case, the feedback voltage V P is the reference voltage V r Therefore, the comparison signal V comp As shown in the figure, the correction signal D ctrl When the resistance of the variable resistor 10c in the high-voltage side resistance cell 10, the resistance of the variable resistor 11c in the low-voltage side resistance cell 11, and the resistance of the variable resistor 12a in the reference cell 12 also decrease, resulting in a decrease in the magnetic feedback current I fb increases.

[0089] That is, in the stabilization section B1, the output signal D 0 Each time the number of cells in the reference cell 12 becomes "2", the comparison signal V compIn response to the magnetic feedback current I fb and the reference current I REF The value is automatically adjusted so that it is equal to the value of the

[0090] In addition, in this stabilization section B1, the magnetic feedback current I fb is the reference current I REF When the feedback voltage V P is the reference voltage V r Therefore, the comparison signal V comp changes to H level (high potential) as shown in the figure.

[0091] Even in this state, as described above, every time the output signal D0 becomes "2", which is the same as the number of the reference cells 12, the comparison signal V comp In response to this, the resistance value of the variable resistor 10c in the high-voltage side resistance cell 10, the resistance value of the variable resistor 11c in the low-voltage side resistance cell 11, and the resistance value of the variable resistor 12a in the reference cell 12 are automatically corrected so that the magnetic feedback current Ifb and the reference current IREF are equal.

[0092] The magnetic sensor A1 and magnetic measurement device C1 according to the first embodiment include a pickup coil 3 (magnetic detection unit) that outputs a detection signal in response to an external magnetic field G, and an output signal D 0 and a signal processing unit 4 for generating an output signal D 0 Based on the feedback current I fb and generates the feedback current I fb and a stabilization unit B1 that stabilizes the signal and outputs it to a pickup coil 3 (magnetic detection unit).

[0093] Therefore, according to the first embodiment, since the stabilizing unit B1 is provided, the output signal D 0 It is possible to provide a magnetic sensor A1 and a magnetic measurement device C1 capable of suppressing fluctuations in the conversion gain to the input signal.

[0094] In the magnetic sensor A1 and the magnetic measuring device C1 according to the first embodiment, the stabilizing unit B1 outputs the output signal D 0 Based on the feedback current I fb and a current generating unit 5 that generates a feedback voltage V P and the reference voltage V r Based on the feedback current I fb and the reference current I REF A comparison unit 6 compares the signal V comp Based on the feedback current I fb is the reference current I REF and a correction signal generating unit 7 that controls the current generating unit 5 so that the current is equal to

[0095] According to the first embodiment, the feedback current I fb is the reference current I REF Since the current generating unit 5 is feedback-controlled by the correction signal generating unit 7 so that the reference current I REF The feedback current I fb It is possible to stabilize the

[0096] In the magnetic sensor A1 and magnetic measurement device C1 according to the first embodiment, the stabilization unit B1 has a pair of current generating units 5 provided on both ends of the pickup coil 3 (magnetic detection unit). Therefore, according to the first embodiment, the feedback current I fb It is possible to stabilize the temperature with high precision.

[0097] In the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment, the comparison unit 6 detects the feedback current I fb and the reference current I REF According to the first embodiment, the feedback current I fb and the reference current I REF When the comparison signal Vcomp It is possible to suppress fluctuations in the

[0098] That is, according to the first embodiment, the correction signal D caused by disturbances, etc. ctrl Therefore, according to the first embodiment, it is possible to stably control the current generating unit 5 by the comparing unit 6, and therefore the feedback current I fb It is possible to further stabilize the above.

[0099] In the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment, the logic circuit 15 (the correction signal generating unit 7) has a dead zone that extends over a predetermined period. fb and the reference current I REF When the comparison signal V comp It is possible to suppress fluctuations in the

[0100] Furthermore, in the magnetic sensor A1 and the magnetic measurement device C1 according to the first embodiment, the output signal is a digital signal, and the current generating unit 5 outputs the output signal D 0 (Digital signal) based on analog signal feedback current I fb Therefore, according to the first embodiment, the output signal D 0 (Digital signal) based on the feedback current I fb It is possible to generate with high accuracy.

[0101] Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. In addition, in Fig. 5, the same components as those in the first embodiment are denoted by the same reference numerals, and the following mainly describes the points that are different from the first embodiment.

[0102] 5, the magnetic sensor A2 according to the second embodiment includes a digital filter 20 and a digital multiplier 21 in addition to the sensor head 1, driving unit 2, pickup coil 3, signal processing unit 4, current generating unit 5, comparing unit 6, and correction signal generating unit 7 in the magnetic sensor A1 according to the first embodiment. Of these components, the comparing unit 6, correction signal generating unit 7, digital filter 20, and digital multiplier 21 configure a stabilization unit B2 in the second embodiment.

[0103] In the magnetic sensor A2 according to the second embodiment, the correction signal D ctrl is supplied to a digital multiplier 21, instead of being supplied to a current generating unit 5 as in the first embodiment. In the magnetic sensor A1 according to the first embodiment, the D / A conversion characteristic (conversion coefficient) of the current generating unit 5 functioning as a D / A converter is adjusted by the correction signal D ctrl The feedback current I fb was stabilized.

[0104] In contrast, the magnetic sensor A2 according to the second embodiment has a correction signal D ctrl Control of the current generating unit 5 using the correction signal D ctrl is supplied to the current generating section 5 to generate a feedback current I fb Instead of directly regulating the feedback current I fb The output signal D due to the fluctuation of 0 Fluctuations in the (digital signal) are corrected by post-processing using a digital filter 20 and a digital multiplier 21 .

[0105] In the magnetic sensor A2, the input terminal of the digital filter 20 is connected to the output terminal of the signal processing unit 4, and the output terminal is connected to the first input terminal of the digital multiplier 21. The digital filter 20 multiplies the output signal D 0 (Digital signal) band-limited output signal D 1 (digital signal) to the digital multiplier 21.

[0106] The digital multiplier 21 has a first input terminal connected to the output terminal of the digital filter 20 and a second input terminal connected to the output terminal of the correction signal generating unit 7. The digital multiplier 21 also has an output terminal connected to an external device. That is, the output terminal of the digital multiplier 21 is the output terminal of the magnetic sensor A2 according to the second embodiment.

[0107] This digital multiplier 21 multiplies the band-limited output signal D 1 (digital signal) and correction signal D ctrl By multiplying with out The correction signal D ctrl is the feedback current I fb Since it is a digital signal that indicates the amount of correction, the correction output signal D out is the feedback current I fb Output signal D due to fluctuations in 0 This suppresses fluctuations in the

[0108] That is, the stabilization unit B2 in the second embodiment uses the correction signal D ctrl Using the feedback current I fb Instead of directly correcting ctrl Based on the feedback current I fb is the reference current I REF The output signal D is equal to 0 This is a method for performing correction processing on the image.

[0109] According to the second embodiment, the stabilization unit B2 is provided with the comparator 6, the correction signal generator 7, the digital filter 20, and the digital multiplier 21, so that the correction output signal D out It is possible to provide a magnetic sensor A2 and a magnetic measurement device C2 capable of suppressing fluctuations in the conversion gain to the input signal.

[0110] Furthermore, according to the second embodiment, it is possible to simplify the analog circuit in the current generating unit 5, and therefore it is possible to reduce the area required for mounting the analog circuit as compared to the first embodiment. Therefore, according to the second embodiment, it is possible to improve the degree of freedom in mounting the circuit in the current generating unit 5.

[0111] Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. In addition, in Fig. 6, the same components as those in the first embodiment are denoted by the same reference numerals, and the following mainly describes the points that are different from the first embodiment.

[0112] 6, the magnetic sensor A3 according to the third embodiment includes a magnetic feedback coil 3a in addition to the sensor head 1, driving unit 2, pickup coil 3, signal processing unit 4, current generating unit 5, comparing unit 6 and correction signal generating unit 7 in the magnetic sensor A1 according to the first embodiment. Note that the stabilizing unit B3 in the third embodiment is the same as the stabilizing unit B1 in the first embodiment.

[0113] In the magnetic sensor A1 according to the first embodiment, the pickup coil 3 generates a feedback current I in addition to a magnetic detection current based on an external magnetic field G. fb The feedback current I fb generates a feedback magnetic field in the pickup coil 3, thereby improving the linearity of the detection characteristics of the external magnetic field G. That is, in the magnetic sensor A1, the pickup coil 3 is used both for detecting the external magnetic field G and for generating the feedback magnetic field.

[0114] In contrast, in the magnetic sensor A2 according to the second embodiment, the feedback current I fb Unlike the first embodiment, power is supplied to the pickup coil 3, but to the magnetic feedback coil 3a. In the magnetic sensor A2 according to the second embodiment, the pickup coil 3 is dedicated to detecting the external magnetic field G, and a feedback magnetic field is generated by the magnetic feedback coil 3a provided separately from the pickup coil 3.

[0115] In the magnetic sensor A2, the magnetic feedback coil 3a is provided in the vicinity of the pickup coil 3 and the sensor head 1. That is, the magnetic feedback coil 3a is a winding that is magnetically coupled with the pickup coil 3.

[0116] One end of the magnetic feedback coil 3a is connected to the output terminal of the current generating unit 5, and the other end is connected to the first input terminal of the current generating unit 5. The feedback current I fb A feedback magnetic field is generated in the vicinity based on this, and this feedback magnetic field is made to act on the pickup coil 3.

[0117] According to the third embodiment, since the stabilizing section B3 is provided, the correction output signal D out It is possible to provide a magnetic sensor A3 and a magnetic measurement device C3 capable of suppressing fluctuations in the conversion gain to the input signal.

[0118] According to the third embodiment, the magnetic feedback coil 3a is provided separately from the pickup coil 3, which increases the number of parts. However, since the pickup coil 3 is dedicated to detecting the external magnetic field G, the freedom of selection of the pickup coil 3 is improved compared to the first embodiment. Also, the problem of parasitic voltage caused by the resistor Rp (parasitic resistance) in FIG. 1 can be avoided.

[0119] [Fourth embodiment] Next, a fourth embodiment of the present invention will be described with reference to Fig. 2 showing the first embodiment. In the magnetic sensor according to the fourth embodiment, the low-voltage side resistive cell 11 of the current generating unit 5 in the first embodiment is eliminated, and the other end of the pickup coil 3 (magnetic detection unit) is grounded.

[0120] That is, the magnetic sensor according to the fourth embodiment has a single-ended type circuit configuration in which a D / A converter is provided only on one side of the pickup coil 3 (magnetic detection unit). For example, the magnetic sensor described in Patent Document 1 has a single-ended type circuit configuration like the magnetic sensor according to the fourth embodiment.

[0121] According to the fourth embodiment, a stabilization section is provided that includes a current generating section from which the comparison section 6, the correction signal generating section 7, and the low-voltage side resistance cell 11 have been removed, so that it is possible to suppress fluctuations in the conversion gain in the same manner as in the first to third embodiments described above.

[0122] The present invention is not limited to the above-described first to fourth embodiments, and the following modified examples are possible. (1) In the above embodiments, the high-voltage side resistor cell 10 and the low-voltage side resistor cell 11 are configured as a resistance-type D / A converter as shown in Fig. 2. However, the current generating unit of the present invention is not limited to this. As the configuration of the high-voltage side resistor cell 10 and the low-voltage side resistor cell 11, for example, a conversion circuit as shown in Fig. 7 is considered.

[0123] The conversion circuit shown in FIG. 7(a) is a current steering type D / A conversion circuit. The conversion circuit shown in FIG. 7(b) is a resistive type D / A converter similar to the first to fourth embodiments. On the other hand, the conversion circuits shown in FIGS. 7(c) and 7(d) are D / A converters of a resistive type similar to the first to fourth embodiments. 0 is an analog signal, not a digital signal, and the correction signal D ctrl The feedback current I fb The current value is adjustable.

[0124] The conversion circuit shown in FIG. 7(c) converts the correction signal D ctrl By variably setting the transfer conductance Gm, the feedback current I fb On the other hand, the conversion circuit shown in FIG. ctrl The resistance value of the resistor is variably set by the resistor resistor R1, thereby adjusting the current value of the feedback current Ifb.

[0125] The conversion circuits in FIG. 7(a) and FIG. 7(c) can increase the output impedance, which reduces the induced voltage (input voltage V in 7(b) and 7(d) have the advantage that noise can be reduced.

[0126] (2) As a modification of the stabilization section B1 shown in FIG. 2, for example, stabilization sections B4 and B5 shown in FIGS. 8 and 9 are possible. The stabilization unit B4 of FIG. 8 includes N high-voltage side resistor cells 10 as shown in the figure. H , and N low-voltage side resistor cells 11 L , high voltage side reference cell 12 H , low voltage side reference cell 12 L , High voltage side differential amplifier 14 H , Low voltage side differential amplifier 14 L , high voltage side signal circuit 15 H , low voltage side signal circuit 15 L , constant current source 16, high voltage side enable switch 17 H and low voltage side enable switch 17 L It is equipped with:

[0127] Among these components, N high-voltage side resistor cells 10 H , N low-voltage side resistor cells 11 L , High voltage side enable switch 17 H and low voltage side enable switch 17 L The N high-voltage side resistor cells 10 constitute the current generating unit 5 in FIG. H corresponds to the high-voltage side current generator in the present invention, and N low-voltage side resistance cells 11 L corresponds to the low-voltage side current generator in the present invention.

[0128] Also, the high-voltage reference cell 12 H , low voltage side reference cell 12 L , High voltage side differential amplifier 14 H , Low voltage side differential amplifier 14L and constant current source 16 constitute comparison section 6 in FIG. H and low voltage side signal circuit 15 L constitutes the correction signal generating unit 7 in FIG.

[0129] High voltage side resistor cell 10 H and low voltage side resistance cell 11 L is the output signal D of the signal processing unit 4 0 In other words, N high-voltage side resistor cells 10 are provided corresponding to the bit string of the digital signal. H is the output signal D 0 The 0th bit of the high-voltage resistor cell corresponds to the 0th bit of the output signal D 0 The first high-voltage side resistor cell corresponding to the first bit of the 0 The N-1th high-voltage side resistor cell corresponds to the N-1th bit of the N-1th high-voltage side resistor cell.

[0130] N high voltage side resistor cells 10 H All of the N high-voltage side resistor cells 10H have the same circuit configuration. As shown in the figure, each of the N high-voltage side resistor cells 10H includes a high-voltage side switch 10e, a low-voltage side switch 10f, a high-voltage side transistor 10g, a low-voltage side transistor 10h, and a resistor 10i.

[0131] High-voltage side switch 10e is a two-contact open / close switch, with a first contact connected to a DC power supply, a second contact connected to the source terminal of high-voltage side transistor 10g, and a control terminal connected to the control terminal of low-voltage side switch 10f and a low-voltage side resistor cell 11. L the control terminal of the high-voltage side switch 11e and the control terminal of the low-voltage side switch 11f, and the high-voltage side signal circuit 15 H The first input terminal and the low-voltage side signal circuit 15 L is connected to the first input terminal of the

[0132] Further, the control terminal of the high-voltage side switch 10e is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilization unit B4. The high-voltage side switch 10e receives the output signal D0 (digital signal) is input, and this output signal D 0 The open / close state is controlled by (digital signal).

[0133] That is, the high-voltage side switch 10e of the first high-voltage side resistor cell receives the output signal D 0 The open / close state is controlled by the 0th bit of (digital signal), and the high-voltage side switch 10e of the 1st high-voltage side resistor cell is controlled by the output signal D 0 The open / close state is controlled by the first bit of (digital signal), (omitted), and the high-voltage side switch 10e of the (N-1)th high-voltage side resistor cell outputs the output signal D 0 The open / close state is controlled by the (N-1)th bit of the (digital signal).

[0134] The low-voltage side switch 10f is a two-contact open / close switch similar to the high-voltage side switch 10e. The first contact of the low-voltage side switch 10f is connected to the source terminal of the low-voltage side transistor 10h, the second contact is grounded, and the control terminal is connected to the control terminal of the high-voltage side switch 10e and the low-voltage side resistor cell 11. L the control terminal of the high-voltage side switch 11e and the control terminal of the low-voltage side switch 11f, and the high-voltage side signal circuit 15 H The first input terminal and the low-voltage side signal circuit 15 L is connected to the first input terminal of the

[0135] The control terminal of the low-voltage side switch 10f is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilization unit B4. 0 (digital signal) is input, and this output signal D 0 The open / closed state is controlled inversely to that of high-voltage side switch 10e by the inverted sign of the (digital signal).

[0136] That is, the low-voltage side switch 10f of the first highest-voltage side resistance cell receives the output signal D 0The open / close state is controlled by the inversion code of the 0th bit in (digital signal), and the low-voltage side switch 10f of the 1st high-voltage side resistor cell outputs the output signal D 0 The open / close state is controlled by the inverted sign of the first bit in (digital signal), (omitted), and the low-voltage side switch 10f of the (N-1)th high-voltage side resistor cell outputs the output signal D 0 The open / close state is controlled by the inverted sign of the (N-1)th bit in the (digital signal).

[0137] As shown in the figure, the high-voltage side transistor 10g is a P-type MOS transistor. The high-voltage side transistor 10g has a gate terminal connected to the low-voltage side resistor cell 11. L the gate terminal of the high-voltage side transistor 11g in the high-voltage side signal circuit 15 H Output terminal and high voltage side reference cell 12 H The gate terminal of the high-voltage side transistor 12b in the

[0138] The source terminal of high-voltage side transistor 10g is connected to the second contact of high-voltage side switch 10e, and the drain terminal is connected to the drain terminal of low-voltage side transistor 10h and one end of resistor 10i. H The high-voltage side correction signal DH input to the gate terminal from ctrl The resistance between the drain and source terminals is controlled by.

[0139] The low-voltage side transistor 10h is an N-type MOS transistor as shown in the figure. The gate terminal of the low-voltage side transistor 10h is connected to the low-voltage side resistor cell 11. L the gate terminal of the low-voltage side transistor 11h in the low-voltage side signal circuit 15 L output terminal and low voltage side reference cell 12 L The gate terminal of the low-voltage side transistor 12d in the

[0140] The source terminal of low-voltage side transistor 10h is connected to the drain terminal of high-voltage side transistor 10g and one end of resistor 10i, and the drain terminal is connected to the first contact of low-voltage side switch 10f. L The low-voltage side correction signal DL is input to the gate terminal from ctrl The resistance between the drain and source terminals is controlled by.

[0141] The resistor 10i is a resistive element having a predetermined resistance value. One end of the resistor 10i is connected to the drain terminal of the high-voltage side transistor 10g and the drain terminal of the low-voltage side transistor 10h, and the other end is connected to the high-voltage side enable switch 17. H Also, the N high-voltage side resistor cells 10 are connected to the first contacts of the H The other ends of the resistors 10i in are all commonly connected as shown in the figure.

[0142] Such a resistor 10i is connected to the output signal D 0 Depending on the open / closed state of high-voltage side switch 10e and low-voltage side switch 10f, which are turned ON (closed) / OFF (open) by a digital signal, one end is connected to a DC power supply via high-voltage side transistor 10g or to ground potential (GND) via low-voltage side transistor 10h.

[0143] On the other hand, N low-voltage side resistor cells 11 L All of the N low-voltage side resistor cells 11 have the same circuit configuration. L As shown in the figure, the inverter circuit 11 includes a high-voltage side switch 11e, a low-voltage side switch 11f, a high-voltage side transistor 11g, a low-voltage side transistor 11h, and a resistor 11i.

[0144] The high-voltage side switch 11e is a two-contact open / close switch, with a first contact connected to a DC power supply, a second contact connected to a source terminal of the high-voltage side transistor 11g, and a control terminal connected to the control terminal of the low-voltage side switch 11f and the high-voltage side resistor cell 10. HThe control terminal of the high-voltage side switch 10e and the control terminal of the low-voltage side switch 10f in the high-voltage side signal circuit 15 H The first input terminal and the low-voltage side signal circuit 15 L is connected to the first input terminal of the

[0145] Further, the control terminal of the high-voltage side switch 11e is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilization unit B4. 0 (digital signal) is input, and this output signal D 0 The open / close state is controlled by (digital signal).

[0146] That is, the high-voltage side switch 11e of the first lowest-voltage side resistance cell receives the output signal D 0 The open / close state is controlled by the 0th bit of (digital signal), and the high-voltage side switch 11e of the 1st low-voltage side resistor cell is controlled by the output signal D 0 The open / close state is controlled by the first bit of (digital signal), (omitted), and the high-voltage side switch 11e of the (N-1)th low-voltage side resistor cell is controlled by the output signal D 0 The open / close state is controlled by the (N-1)th bit of the (digital signal).

[0147] The low-voltage side switch 11f is a two-contact open / close switch similar to the high-voltage side switch 11e. The first contact of the low-voltage side switch 11f is connected to the source terminal of the low-voltage side transistor 11h, the second contact is grounded, and the control terminal is connected to the control terminal of the high-voltage side switch 11e and the high-voltage side resistor cell 10. H The control terminal of the high-voltage side switch 10e and the control terminal of the low-voltage side switch 10f in the high-voltage side signal circuit 15 H The first input terminal and the low-voltage side signal circuit 15 L is connected to the first input terminal of the

[0148] Further, the control terminal of the low-voltage side switch 11f is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilization unit B4. 0 (digital signal) is input, and this output signal D 0 The open / closed state is controlled inversely to that of high-voltage side switch 11e by the inverted sign of the (digital signal).

[0149] That is, the low-voltage side switch 11f of the first low-voltage side resistance cell is connected to the output signal D 0 The open / close state is controlled by the inversion code of the 0th bit in (digital signal), and the low-voltage side switch 11f of the 1st low-voltage side resistor cell outputs the output signal D 0 The open / close state is controlled by the inverted sign of the first bit in (digital signal), (omitted), and the low-voltage side switch 11f of the (N-1)th low-voltage side resistor cell outputs the output signal D 0 The open / close state is controlled by the inverted sign of the (N-1)th bit in the (digital signal).

[0150] As shown in the figure, the high-voltage side transistor 11g is a P-type MOS transistor. H The gate terminal of the high-voltage side transistor 10g in the low-voltage side signal circuit 15 L output terminal and low voltage side reference cell 12 L The gate terminal of the low-voltage side transistor 12d in the

[0151] The source terminal of the high-voltage side transistor 11g is connected to the second contact of the high-voltage side switch 11e, and the drain terminal is connected to the drain terminal of the low-voltage side transistor 11h and one end of the resistor 11i. L The low-voltage side correction signal DL is input to the gate terminal from ctrl The resistance between the drain and source terminals is controlled by.

[0152] The low-voltage side transistor 11h is an N-type MOS transistor as shown in the figure. The gate terminal of the low-voltage side transistor 11h is connected to the high-voltage side resistor cell 11. H The gate terminal of the low-voltage side transistor 10h in the low-voltage side signal circuit 15 L output terminal and low voltage side reference cell 12 L The gate terminal of the low-voltage side transistor 12d in the

[0153] The source terminal of the low-voltage side transistor 11h is connected to the drain terminal of the high-voltage side transistor 11g and one end of the resistor 11i, and the drain terminal is connected to the first contact of the low-voltage side switch 11f. L The low-voltage side correction signal DL is input to the gate terminal from ctrl The resistance between the drain and source terminals is controlled by.

[0154] The resistor 11i is a resistive element having a predetermined resistance value. One end of the resistor 11i is connected to the drain terminal of the high-voltage side transistor 11g and the drain terminal of the low-voltage side transistor 11h, and the other end is connected to the drain terminal of the low-voltage side enable switch 17. L The N low-voltage side resistor cells 11 are connected to the first contacts of the N low-voltage side resistor cells 11. L The other ends of the resistors 11i in are all commonly connected as shown in the figure.

[0155] Such a resistor 11i is connected to the output signal D 0 Depending on the open / closed state of high-voltage side switch 11e and low-voltage side switch 11f, which are turned ON (closed) / OFF (open) by a digital signal, one end is connected to a DC power supply via high-voltage side transistor 11g or to ground potential (GND) via low-voltage side transistor 11h.

[0156] High voltage side reference cell 12 HThe high-voltage side transistor 12b includes a high-voltage side transistor 12b and a resistor 12c. As shown in the figure, the high-voltage side transistor 12b is a P-type MOS transistor. The high-voltage side transistor 12b has a gate terminal connected to the high-voltage side resistor cell 10. H The gate terminal of the high-voltage side transistor 10g in the low-voltage side resistor cell 11 L The gate terminal of the high-voltage side transistor 11g and the high-voltage side signal circuit 15 H is connected to the output terminal of the

[0157] The source terminal of the high-voltage transistor 12b is connected to a DC power supply, and the drain terminal is connected to one end of a resistor 12c. The resistor 12c is a two-terminal element having a predetermined resistance value. One end of the resistor 12c is connected to the drain terminal of the high-voltage transistor 12b, and the other end is connected to the high-voltage differential amplifier 14. H and an input terminal of a constant current source 16.

[0158] Such a high-voltage side reference cell 12 H In the high-voltage side transistor 12b, the high-voltage side signal circuit 15 H The high-voltage side correction signal DH input to the gate terminal from ctrl The resistance value between the drain and source terminals changes based on the voltage Vcc of the high-voltage side transistor 12b. One end of the resistor 12c is connected to the DC power supply when the high-voltage side transistor 12b is turned on (conductive).

[0159] Low voltage reference cell 12 L The low-voltage side transistor 12d includes a low-voltage side transistor 12d and a resistor 12e. As shown in the figure, the low-voltage side transistor 12d is an N-type MOS transistor. The low-voltage side transistor 12d has a gate terminal connected to the high-voltage side resistor cell 10. H The gate terminal of the low-voltage side transistor 10h in the low-voltage side resistor cell 11 L The gate terminal of the low-voltage side transistor 11h and the low-voltage side signal circuit 15 L is connected to the output terminal of the

[0160] The drain terminal of the low-voltage side transistor 12d is connected to one end of a resistor 12e, and the source terminal is grounded. The resistor 12e is a two-terminal element having a predetermined resistance value. One end of the resistor 12e is connected to the drain terminal of the low-voltage side transistor 12d, and the other end is connected to the low-voltage side differential amplifier 14. L and the output terminal of a constant current source 16.

[0161] Such a low-voltage side reference cell 12 L In the low-voltage side transistor 12d, L The low-voltage side correction signal DL is input to the gate terminal from ctrl The resistance value between the drain and source terminals changes based on the voltage Vref of the low-voltage side transistor 12d. One end of the resistor 12e is grounded when the low-voltage side transistor 12d is turned on (conducting).

[0162] That is, in the stabilization section B4 according to this modification, the high-voltage side reference cell 12 H The high-voltage side transistor 12b and the low-voltage side reference cell 12 L By biasing both of the low-voltage side transistors 12b and 12d, a current path is formed from the DC power supply to the high-voltage side transistor 12b, resistor 12c, constant current source 16, resistor 12e, low-voltage side transistor 12d, and ground potential (GND).

[0163] High voltage side differential amplifier 14 H The high-voltage side differential amplifier 14 is a three-terminal element having a first input terminal (negative phase input terminal), a second input terminal (positive phase input terminal), and an output terminal. H is the high-voltage reference voltage VH applied to the first input terminal (negative phase input terminal). r and the high-voltage feedback voltage V applied to the second input terminal (positive input terminal) P The error signal obtained by amplifying the difference between the high voltage side comparison signal VH comp As high voltage side signal circuit 15 H Output to.

[0164] Low voltage side differential amplifier 14 LThe high-voltage differential amplifier 14 H Similarly, the low-voltage side differential amplifier 14 is a three-terminal element having a first input terminal (negative phase input terminal), a second input terminal (positive phase input terminal), and an output terminal. L is the low-voltage reference voltage VL applied to the first input terminal (negative phase input terminal). r and the low-voltage feedback voltage V applied to the second input terminal (positive input terminal) N The error signal obtained by amplifying the difference between the low-voltage side comparison signal VL comp Low voltage side signal circuit 15 L Output to.

[0165] High voltage side signal circuit 15 H This is an analog circuit with two inputs and one output. H The first input terminal is a high-voltage side resistor cell 10 H The control terminal of the high-voltage side switch 10e and the control terminal of the low-voltage side switch 10f, the low-voltage side resistive cell 11 L The control terminal of the high-voltage side switch 11e and the control terminal of the low-voltage side switch 11f and the low-voltage side logic circuit 15 L is connected to the first input terminal of the

[0166] In addition, the high voltage side signal circuit 15 H The first input terminal of the high-voltage side signal circuit 15 is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilizing unit B4. H The second input terminal is the high-voltage side differential amplifier 14 H is connected to the output terminal of the

[0167] Furthermore, this high voltage side signal circuit 15 H The output terminal is the high-voltage side resistor cell 10 H The gate terminal of the high-voltage side transistor 10g in the low-voltage side resistor cell 11 L The gate terminal of the high-voltage side transistor 11g and the high-voltage side reference cell 12 H The gate terminal of the high-voltage side transistor 12b in the

[0168] This high voltage side signal circuit 15 H is the output signal D input from the signal processing unit 4 to the first input terminal 0 (Digital signal) and high voltage side differential amplifier 14 H The high-voltage comparison signal VH is input to the second input terminal from comp By performing logical processing on the high voltage side correction signal DH ctrl This high-voltage side correction signal DH ctrl is the feedback current I fb is an analog signal indicating the amount of correction.

[0169] This high voltage correction signal DH ctrl is a control signal for controlling the high-voltage side transistor 10g, the high-voltage side transistor 11g, and the high-voltage side transistor 12b. H , low voltage side resistor cell 11 L and high voltage side reference cell 12 H will be output.

[0170] Low voltage side signal circuit 15 L The high-voltage side signal circuit 15 H This is an analog circuit with two inputs and one output, just like the low-voltage side signal circuit 15 L The first input terminal is a high-voltage side resistor cell 10 H The control terminal of the high-voltage side switch 10e and the control terminal of the low-voltage side switch 10f, the low-voltage side resistive cell 11 L The control terminal of the high-voltage side switch 11e and the control terminal of the low-voltage side switch 11f and the high-voltage side logic circuit 15 H is connected to the first input terminal of the

[0171] In addition, the low-voltage side signal circuit 15 L The first input terminal of the low-voltage side signal circuit 15 is connected to the output terminal of the signal processing unit 4 and the second input terminal of the current generating unit 5 outside the stabilizing unit B4. L The second input terminal is a low-voltage side differential amplifier 14 L is connected to the output terminal of the

[0172] Furthermore, this low-voltage side signal circuit 15L The output terminal is the high-voltage side resistor cell 10 H The gate terminal of the low-voltage side transistor 10h in the low-voltage side resistor cell 11 L The gate terminal of the low-voltage side transistor 11h and the low-voltage side reference cell 12 L The gate terminal of the low-voltage side transistor 12d in the

[0173] This low-voltage side signal circuit 15 L is the output signal D input from the signal processing unit 4 to the first input terminal 0 (Digital signal) and low voltage side differential amplifier 14 L The low-voltage side comparison signal VL is input to the second input terminal from comp By carrying out a predetermined logical process on the low voltage side correction signal DL ctrl This low-voltage side correction signal DL ctrl is the high voltage side correction signal DH ctrl Similarly, the feedback current I fb is an analog signal indicating the amount of correction.

[0174] This low-voltage side correction signal DL ctrl is a control signal for controlling the low-voltage side transistor 10h, the low-voltage side transistor 11h, and the low-voltage side transistor 12d. H , low voltage side resistor cell 11 L and low voltage side reference cell 12 L will be output.

[0175] The constant current source 16 is a two-terminal element having an input terminal and an output terminal. H The other end of resistor 12c and the high voltage side differential amplifier 14 H The output terminal is connected to the first input terminal (negative phase input terminal) of the low-voltage side reference cell 12 L The other end of resistor 12e and the low-voltage side differential amplifier 14 L The first input terminal (inverted phase input terminal) of the amplifier is connected to the first input terminal (inverted phase input terminal) of the amplifier.

[0176] The input terminal of the constant current source 16 is connected to a DC power supply via a resistor 12c, and the output terminal is connected to a ground potential (GND) via a resistor 12e, so that a constant reference current I flows from the input terminal to the output terminal. REF That is, the constant current source 16 supplies the high-voltage side reference cell 12 connected in series with itself with H Resistor 12c and low-voltage side reference cell 12 L The reference current I REF Turn on the power.

[0177] As shown in the figure, the input terminal of the constant current source 16 is connected to a high-voltage reference voltage VH r The output terminal of the constant current source 16 is connected to the low-voltage reference voltage VL r The high voltage reference voltage VH r is the power supply voltage V cc is the resistance value R of resistor 12c H and the sum of the resistance value of the high-voltage side transistor 12b and the reference current I REF The voltage is the voltage that is dropped by the voltage multiplied by the low-voltage reference voltage VL r The ground potential (=0) is the resistance R of resistor 12e. L and the sum of the resistance value of the voltage side transistor 12d and the reference current I REF The voltage is increased by the voltage multiplied by

[0178] High voltage side enable switch 17 H This high-voltage side enable switch 17 is a two-contact open / close switch. H The first contacts are N high-voltage side resistor cells 10 H The second contact is connected to the high-voltage side differential amplifier 14 H and one end of the pickup coil 3.

[0179] In addition, this high-voltage side enable switch 17 H The control terminal of the high-voltage side enable switch 17 is connected to an external control device (not shown). HThe open / close state of the switch is controlled by an enable signal EN input to the control terminal. As described in the first embodiment, the enable signal EN is fb This is a control signal that turns on (power supply) / off (power non-supply) the power supply to the pickup coil 3.

[0180] Low voltage side enable switch 17 L High voltage side enable switch 17 H This low-voltage side enable switch 17 is a two-contact open / close switch similar to that shown in FIG. L The first contacts are N low-voltage side resistor cells 11 L The second contact is connected to the other end of the low-voltage side differential amplifier 14 L and the other end of the pickup coil 3.

[0181] In addition, this low-voltage side enable switch 17 L High voltage side enable switch 17 H The low-voltage side enable switch 17 is connected to an external control device in the same manner as the low-voltage side enable switch 17. L The open / close state of the switch is controlled by an enable signal EN input to the control terminal. This enable signal EN controls the magnetic feedback current I fb This is a control signal that turns on (power supply) / off (power non-supply) the power supply to the pickup coil 3.

[0182] In such a stabilization section B4, the high-voltage side resistor cell 10 H and low voltage side resistance cell 11 L are configured as resistance-type D / A converters similar to the high-voltage side resistance cell 10 and the low-voltage side resistance cell 11 in the stabilization unit B1 of the first embodiment.

[0183] In addition, in the stabilization section B4, the high-voltage comparison signal VH comp is the high voltage reference voltage VH r and the high-side feedback voltage V P and the low-voltage comparison signal VL compis the low voltage reference voltage VL r and the low-side feedback voltage V N This is the comparison result.

[0184] And the high voltage comparison signal VH comp and the output signal D of the signal processor 4 0 (digital signal) and the high-voltage side correction signal DH ctrl is the high-side feedback voltage V P and the high voltage reference voltage VH r and the magnetic feedback current I fb is the reference current I REF High voltage side resistance cell 10 H and low voltage side resistance cell 11 L is feedback controlled.

[0185] In addition, the low voltage comparison signal VL comp and the output signal D of the signal processor 4 0 (digital signal) and the low-voltage side correction signal DL generated based on ctrl is the low-side feedback voltage V N and the low voltage reference voltage VL r and the magnetic feedback current I fb is the reference current I REF High voltage side resistance cell 10 H and low voltage side resistance cell 11 L is feedback controlled.

[0186] According to such a stabilization unit B4, the number of necessary circuit elements (area) increases in comparison with the stabilization unit B1 in the first embodiment, but the output signal D o It is possible to stabilize the conversion gain to with higher precision.

[0187] (3) The stabilization unit B5 in FIG. 9 stabilizes the output signal D 0 This corresponds to the case where the output signal D in the stabilization section B5 is an analog signal, not a digital signal. 0is the positive-phase analog signal, the positive-phase output signal D 0 Inverted output signal D, which is an analog signal inverted from (+) 0 (-) is included.

[0188] As shown in FIG. 9 , the stabilization unit B5 includes an operational amplifier 30, a reference resistance transistor 31, a resistor 32, a constant current source 33, a high-voltage side resistance transistor 34, a low-voltage side resistance transistor 35, a high-voltage side resistor 36, a high-voltage side enable switch 37, a low-voltage side resistor 38, and a low-voltage side enable switch 39.

[0189] The operational amplifier 30 is a three-terminal element having a first input terminal (positive-phase input terminal), a second input terminal (negative-phase input terminal), and an output terminal. The first input terminal (positive-phase input terminal) of this operational amplifier 30 is connected to a second reference voltage source (not shown), and the second input terminal (negative-phase input terminal) is connected to one terminal of a resistor 32 and an input terminal of a constant current source 33. The second reference voltage source is a second reference voltage V REF2 is output to the first input terminal (positive phase input terminal) of the operational amplifier 30.

[0190] Moreover, the output terminal of this operational amplifier 30 is connected to the gate terminal of the amplifying transistor 31, the gate terminal of the high-voltage side transistor 34, and the gate terminal of the low-voltage side transistor 35. Such an operational amplifier 30 amplifies the difference (error) between a first voltage applied to a first input terminal (positive phase input terminal) and a second voltage applied to a second input terminal (negative phase input terminal), and outputs an error voltage V G The output is as follows:

[0191] As shown in the figure, the amplifying transistor 31 is an N-type MOS transistor. The gate terminal of this amplifying transistor 31 is connected to the output terminal of the operational amplifier 30, the gate terminal of the high-voltage side transistor 34, and the gate terminal of the low-voltage side transistor 35.

[0192] The amplifier transistor 31 has a drain terminal connected to a first reference voltage source (not shown) and a source terminal connected to the other end of the resistor 32. The first reference voltage source supplies a first reference voltage VREF1 is output to the drain terminal of the amplifying transistor 31. Such an amplifying transistor 31 amplifies the current of the output of the operational amplifier 30.

[0193] Resistor 32 is a two-terminal element having a predetermined resistance value. One end of resistor 32 is connected to the second input terminal (inverting input terminal) of operational amplifier 30 and the input terminal of constant current source 33, and the other end is connected to the source terminal of amplifying transistor 31. Resistor 32 is a circuit element for dropping voltage, and its resistance value is set to the same value as the resistance value of high-voltage side resistor 36 and the resistance value of low-voltage side resistor 38.

[0194] The constant current source 33 is a two-terminal element having an input terminal and an output terminal. The input terminal of this constant current source 33 is connected to the second input terminal (inverting input terminal) of the operational amplifier 30 and one terminal of the resistor 32, and the output terminal is grounded. The input terminal of this constant current source 33 is connected to the first reference voltage source via the amplifying transistor 31 and the resistor 32, and a constant reference current I REF Flush.

[0195] High-voltage side transistor 34 is an N-type MOS transistor biased in the linear region, similar to amplifying transistor 31. The gate terminal of high-voltage side transistor 34 is connected to the output terminal of operational amplifier 30, the gate terminal of amplifying transistor 31, and the gate terminal of low-voltage side transistor 35. In addition, the drain terminal of high-voltage side transistor 34 is connected to the positive phase output terminal of signal processing unit 4, and the source terminal is connected to one end of high-voltage side resistor 36.

[0196] Such a high-voltage side transistor 34 receives a positive-phase output signal D 0 (+), the resistance value of the high-voltage resistor 36 whose one end is connected to the source terminal, and the error voltage V applied to the gate terminal G Based on the source current (magnetic feedback current I fb ) is set.

[0197] Low-voltage side transistor 35 is an N-type MOS transistor similar to high-voltage side transistor 34. The gate terminal of low-voltage side transistor 35 is connected to the output terminal of operational amplifier 30, the gate terminal of amplifying transistor 31, and the gate terminal of high-voltage side transistor 34. In addition, the drain terminal of low-voltage side transistor 35 is connected to the inverted output terminal of signal processing unit 4, and the source terminal is connected to one end of low-voltage side resistor 38.

[0198] Such a low-side transistor 35 receives an inverted output signal D 0 (-), the resistance value of the low-voltage resistor 38 whose one end is connected to the source terminal, and the error voltage V applied to the gate terminal G Based on the source current (magnetic feedback current I fb ) is set.

[0199] High-voltage side resistor 36 is a two-terminal element having a predetermined resistance value. One end of high-voltage side resistor 36 is connected to the source terminal of high-voltage side transistor 34, and the other end is connected to the first contact of high-voltage side enable switch 37. High-voltage side resistor 36 flows magnetic feedback current I together with the source current of high-voltage side transistor 34 as described above. fb This sets the following.

[0200] High-voltage side enable switch 37 is a two-contact open / close switch as shown in the figure. High-voltage side enable switch 37 has a first contact connected to the other end of high-voltage side resistor 36 and a second contact connected to one end of pickup coil 3.

[0201] The high-voltage side enable switch 37 has a control terminal connected to an external control device (not shown). The open / close state of the high-voltage side enable switch 37 is controlled by an enable signal EN input to the control terminal from the external control device. As described in the first embodiment, the enable signal EN is a magnetic feedback current I fbThis is a control signal that turns on (power supply) / off (power non-supply) the power supply to the pickup coil 3.

[0202] Low-voltage side resistor 38 is a two-terminal element having a predetermined resistance value. One end of low-voltage side resistor 38 is connected to the source terminal of low-voltage side transistor 35, and the other end is connected to the first contact of low-voltage side enable switch 39. Low-voltage side resistor 38 flows magnetic feedback current I together with the source current of low-voltage side transistor 35 as described above. fb The resistance value is set to the same value as the resistance value of resistor 32 and the resistance value of high-voltage side resistor 36.

[0203] Low-voltage side enable switch 39 is a two-contact open / close switch like high-voltage side enable switch 37. This low-voltage side enable switch 39 has a first contact connected to the other end of low-voltage side resistor 38 and a second contact connected to the other end of pickup coil 3.

[0204] The control terminal of low-voltage side enable switch 39 is connected to an external control device (not shown). The open / close state of low-voltage side enable switch 39 is controlled by an enable signal EN input to the control terminal from the external control device, similar to high-voltage side enable switch 37.

[0205] In such a stabilization section B5, the resistance value of resistor 32, the resistance value of high-voltage side resistor 36, and the resistance value of low-voltage side resistor 38 are set to the same value, so that an appropriate error voltage V G By controlling the resistance values ​​of the amplifying transistor 31, the high-voltage side transistor 34, and the low-voltage side transistor 35 through (the output voltage of the operational amplifier 30), the magnetic feedback current I fb is the reference current I REF That is, the error voltage V of the operational amplifier 30 is controlled to be equal to G is the magnetic feedback current I fb is the reference current I REFThe gate voltages of the high-voltage side transistor 34 and the low-voltage side transistor 35 are feedback-controlled so as to match

[0206] According to such a stabilization unit B5, the output signal D of the signal processing unit 4 0 is the positive phase output signal D 0 (+) and inverse phase output signal D 0 Even in the case of a balanced analog signal consisting of (-) and (-), a relatively simple circuit configuration can be used to output the output signal D from the external magnetic G. o It is possible to stabilize the conversion gain to

[0207] (4) FIG. 10 shows a modification of the current generating unit 5. The current generating unit B6 according to this modification converts the output signal D 0 This corresponds to the case where the bit length of the digital signal is 1 bit. As shown in FIG. 10, the current generating unit B6 includes a high-voltage side shift register 40 H , a plurality of high-side switches 41 H , a plurality of high-voltage side variable resistors 42 H , low-voltage side shift register 40 L , a plurality of low-side switches 41 L and a plurality of low-voltage side variable resistors 42 L It is equipped with:

[0208] High-side shift register 40 H is a digital circuit in which multiple D flip-flop circuits are cascaded as shown in the figure, and the output signal D 0 is used as an input signal. H outputs an output signal D based on a separately input clock signal (not shown). 0 is passed from the previous D flip-flop circuit to the next D flip-flop circuit.

[0209] FIG. 10 shows an example of a five-stage shift register in which five D flip-flop circuits are cascade-connected. H is a 1-bit output signal D 0The high-voltage side shift register 40 has a function of converting the input voltage Vcc to a 5-bit binary code. H The number of stages is not limited to five.

[0210] Multiple high-side switches 41 H is a two-contact open / close switch having a first contact and a second contact. H is the high-voltage side shift register 40 H The first contacts are provided corresponding to the plurality of D flip-flop circuits in the first input / output terminal 111 and each first contact is connected to the output terminal of the corresponding D flip-flop circuit.

[0211] In addition, multiple high-voltage side switches 41 H A plurality of high-voltage side variable resistors 42 each having a second contact corresponding to a plurality of D flip-flop circuits. H Further, a plurality of high-side switches 41 are connected to one end of the H Each control end of the low-voltage side switch 41 L and an enable signal EN is applied to them in common.

[0212] That is, an arbitrary D flip-flop circuit and a high-voltage side variable resistor 42 corresponding to the D flip-flop circuit H There is one high-side switch 41 between H Each D flip-flop circuit and high-voltage variable resistor 42 H The connection relationship between them is controlled by an enable signal EN.

[0213] Multiple high voltage variable resistors 42 H are two-terminal resistor elements having a predetermined resistance variable range. H is the high-voltage side shift register 40 H A plurality of D flip-flop circuits and a plurality of high-voltage side switches 41 in H , and one end of each of them is provided corresponding to the high-voltage side switch 41 H is connected to the second contact of the

[0214] In addition, a plurality of high-voltage side variable resistors 42 H The other ends of the high-voltage side variable resistors 42 are all connected together and to one end of the pickup coil 3. H Each control end is a plurality of low-voltage side variable resistors 42 L and is connected to the output terminal of the correction signal generating unit 7. H is a correction signal D inputted in common to each control terminal from the correction signal generating unit 7. ctrl The resistance value is variably set based on the above.

[0215] Low-voltage side shift register 40 L is the high-voltage side shift register 40 H This low-voltage side shift register 40 is a digital circuit in which D flip-flop circuits having the same number of stages as those in the low-voltage side shift register 40 are cascaded. L is the high-voltage side shift register 40 H Similarly, the output signal D 0 The input signal is the low-voltage side shift register 40. L is the high-voltage side shift register 40 H Similarly, the output signal D 0 is passed from the previous D flip-flop circuit to the next D flip-flop circuit.

[0216] Multiple low-side switches 41 L is a two-contact open / close switch having a first contact and a second contact. L The low-voltage side shift register 40 L The first contacts are provided corresponding to the plurality of D flip-flop circuits in the first input / output terminal 111 and each first contact is connected to the output terminal of the corresponding D flip-flop circuit.

[0217] In addition, a plurality of low-side switches 41 L Each second contact is connected to the low-voltage side shift register 40 L Multiple low-voltage side variable resistors 42 corresponding to the D flip-flop circuit LFurther, a plurality of low-side switches 41 are connected to one end of the L Each control end of the high-voltage side switch 41 H and an enable signal EN is applied to them in common.

[0218] That is, the low-voltage side shift register 40 L Any D flip-flop circuit in and the low-voltage side variable resistor 42 corresponding to the D flip-flop circuit L There is one low-side switch 41 between L Each D flip-flop circuit and low-voltage variable resistor 42 L The connection relationship between them is controlled by an enable signal EN.

[0219] A plurality of low-voltage side variable resistors 42 L is a two-terminal resistor element having a predetermined resistance variable range. L The low-voltage side shift register 40 L A plurality of D flip-flop circuits and a plurality of low-side switches 41 in L , and one end of each of them is provided corresponding to the low-voltage side switch 41 L is connected to the second contact of the

[0220] In addition, a plurality of low-voltage side variable resistors 42 L The other ends of the low-voltage side variable resistors 42 are all connected together and to the other end of the pickup coil 3. L Each control end is a plurality of high-voltage side variable resistors 42 H and the output terminal of the correction signal generating unit 7. L is a correction signal D inputted in common to each control terminal from the correction signal generating unit 7. ctrl The resistance value is variably set based on the above.

[0221] In such a current generating section B6, a plurality of high-voltage side variable resistors 42 Hand a plurality of low-voltage side variable resistors 42 L The resistance value of the correction signal DL of the correction signal generating unit 7 ctrl Therefore, according to the current generating section B6, the output signal D of the signal processing section 4 0 Even if the bit length of is 1 bit, the output signal D o It is possible to stabilize the conversion gain to

[0222] (5) In the above embodiment, the magnetic measuring device that measures biomagnetism as an external magnetic field G has been described, but the present invention is not limited thereto. The magnetic measuring device according to the present invention is capable of detecting various external devices other than biomagnetism with low power consumption and high accuracy. [Explanation of symbols]

[0223] A1~A3 Magnetic sensors B1~B5 Stabilization part B6 Current generation section C1 Magnetic measurement device G External magnetic field 1 Sensor head 2 Drive unit 3 Pickup coil 3a Magnetic feedback coil 4. Signal Processing Section 5 Current generation section 6 Comparison section 7. Correction signal generator 10, 10 H High voltage side resistance cell (high voltage side current generator) 11, 11 L Low-voltage side resistive cell (low-voltage side current generator) 12 Reference Cell 12 H High voltage side reference cell 12 L Low voltage reference cell 13 Constant current source 14 Comparator 14 H High Voltage Side Differential Amplifier 14 L Low Voltage Side Differential Amplifier 15 Logic Circuits 15 H High voltage side signal circuit 15 L Low voltage side signal circuit 16 constant current source 17 H High voltage side enable switch 17 L Low voltage side enable switch 20 Digital Filter 21 Digital Multiplier 30 Operational Amplifier 31 Amplifying transistor 32 resistor 33 Constant current source 34 High voltage side transistor 35 Low-voltage side transistor 36 High voltage resistor 37 High voltage side enable switch 38 Low voltage resistor 39 Low voltage side enable switch 40 H High-side shift register 40 L Low-voltage side shift register 41 H High voltage side switch 41 L Low Side Switch 42 H High voltage side variable resistor 42 L Low voltage side variable resistor

Claims

1. a magnetic detection unit that outputs a detection signal in response to an external magnetic field; a signal processing unit that performs a predetermined signal processing on the detection signal to generate an output signal; a stabilization unit that includes a current generation unit that generates a feedback current based on the output signal and outputs the feedback current to the magnetic detection unit, and that suppresses fluctuations in conversion gain from the external magnetic field to the output signal; A magnetic sensor comprising:

2. The stabilizing portion includes: a comparison unit that compares the feedback current with a predetermined reference current; a correction signal generating unit that generates a correction signal for suppressing a variation in the conversion gain based on a comparison result of the comparing unit; 2. The magnetic sensor according to claim 1, further comprising:

3. 3. The magnetic sensor according to claim 2, wherein the stabilizing section controls the current generating section based on the correction signal so that the feedback current becomes equal to the reference current.

4. 3. The magnetic sensor according to claim 2, wherein the stabilizing section performs a correction process on the output signal based on the correction signal so that the feedback current becomes equal to the reference current.

5. The current generating unit is a high-voltage side current generator connected to a high-voltage side of the magnetic detection unit and configured to generate the feedback current based on the output signal; a low-voltage side current generator connected to a low-voltage side of the magnetic detection unit and configured to generate the feedback current based on the output signal; 3. The magnetic sensor according to claim 1, further comprising:

6. the output signal is a digital signal; 3. The magnetic sensor according to claim 1, wherein the current generating section generates the feedback current by performing digital-to-analog conversion of the output signal.

7. 5. The magnetic sensor according to claim 3, wherein the comparison section has a hysteresis characteristic in the comparison between the feedback current and the reference current.

8. 4. The magnetic sensor according to claim 2, wherein the correction signal generating section has a dead zone that extends over a predetermined period.

9. The magnetic detection unit includes: A pickup coil for detecting the external magnetic field; a magnetic feedback coil through which the feedback current is passed; 3. The magnetic sensor according to claim 1, further comprising:

10. 3. The magnetic sensor according to claim 1, wherein the magnetic detection portion is a magnetic impedance element.

11. The magnetic sensor according to claim 1 or 2, a magnetic measurement unit that measures the external magnetic field using the output signal; A magnetic measuring device comprising:

12. The magnetic measuring device according to claim 11, wherein the external magnetic field is a biomagnetic field generated in a living body.

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